Using 7 way round trailer plug as power source for electric winch

[Starcraft Enterprise]

Has anybody ever tried using their 7 way round tow vehicles 12 volt "Trailer tow battery charge relay" hot lead as a power source for there boat trailers electric winch?
The fuse and relay in the tow vehicle is rated for 30 amps and the internal circuit breaker on my winch is rated for 30 amps. Sounds like a good match.
I was going to make up an adapter where the 7 way round stays plugged into the vehicle when the trailer is submerged, but off of the back of the trailer 7 way, add a 4 way to unplug for the trailer lights.
Maybe add a 20 or 25 amp quick trip breaker inline to trip first before the vehicle fuse blows?

 

[smokeonthewater]

Re: Using 7 way round trailer plug as power source for electric winch

I wouldn't... I would run a heavier guage wire .... at least 4 guage.... but then I may be picturing a bigger winch than you have

If you still want to try it forget basing the decision on the breaker size. While that does matter it is more important to look at load (max continuous amps) wire guage and length..... without these figures you are just guessing

 

[RepoMan207]

Re: Using 7 way round trailer plug as power source for electric winch

If your using one of these style plugs....your more then fine.

 

[Starcraft Enterprise]

Re: Using 7 way round trailer plug as power source for electric winch

Yes, thats the plug I am talking about.

 

[H20Rat]

Re: Using 7 way round trailer plug as power source for electric winch

Those connectors are rated at 15 amps per connection, max of 40 amps for the entire assembly.

Those are the stated SUSTAINED amps, since you never really use a winch for very long you probably would be fine. As others mentioned, the wiring going to the socket is probably sub-par at best. I wouldn't at all be surprised to see 12 gauge wire. The +12v constant line might also be fused at 15 amps.

 

[dingbat]

Re: Using 7 way round trailer plug as power source for electric winch

I looked into this when I wired my winch. You need 40 amps at the motor, not at the battery. Way, way too much current drop with the size of wire they us on that connection. I ended up running 6 gauge cable from the battery back to the bumper. In hindsight I should have used 4 gauge.

 

[TerryMSU]

Re: Using 7 way round trailer plug as power source for electric winch

Close... Your final solution (4 gauge wire) is probably correct. However, the current is the same at both points. What you lose is voltage. Thus you might have 13.8 volts at the battery, but by the time it gets back to the motor the volatge has dropped to (for example) 10 volts. The way that I explain it is like this...

Compare it to plumbing... Voltage is like water pressure. Current (Amps) is like water flow. Thus the water pressure drops along the pipe when you draw a lot of water. If you need to draw a lot of water down a long hose, you get a bigger hose. Electricity behaves quite similar at least as a way to understand its flow. If you need to draw a lot of current, you better get big wire and a connector with big pins. As far as that specific connector, I can't say one way or another if it can handle the current. Look up the current draw on the winch. Then compare it with what the connector is rated for. As far as Smokingcrater's comment on sustained current draw, I would tend to say that your draw may be sustained. Several minutes to winch in a boat is sustained. Again, the definition of "sustained" is subject to interpretation.

TerryMSU

TerryMSU

 

[109jb]

Re: Using 7 way round trailer plug as power source for electric winch

Before we go rewiring his entire truck lets consider a few things.

First - If the circuit is properly protected there isn't a danger of wire damage.

Second - Irregardless of what the winch is rated for the actual current draw will be determined by what is actually be pulled. I assume he will be using the electric winch to pull a 1969 18' Starcraft Starchief, 120 I/O Mercruiser as in his signature. Not exacly an 8000 pound beast.

Personally, I would try what he is suggesting and possibly put a 20 amp fuse inline to see if I were drawing anywhere close to the what the circuit is fused for on the truck. Sure would be cheaper and easier than routing a wire all the from the front of the truck to the back

 

[Starcraft Enterprise]

Re: Using 7 way round trailer plug as power source for electric winch

Boat and trailer together weigh 2,900 lbs. So, 2,000 pounds for the boat?
When I get home tonight, I will check the wire size to the back of the plug on the truck. If it is at least 10 gauge, then will proceed by hooking the winch up with the current method (cables and alligator clips) and put an amp meter in line. Then I will spool out some winch cable and run it with a moderate load up to a stall and see how many amps it draws. If it stays under 30 amps, then I will go ahead with wiring it up to the plug and see what happens.
If it blows the quick trip breaker when I try to retrieve my boat, then I know.
If the wiring on the truck is too small or current draw too high, then I will instal a small battery (lawn mower battery?) on the trailer and just use the power from the 7 pin plug to keep the battery charged. If I leave the truck running while winching, I think I should have plenty of battery.
Apparently I am the first to try this, during my searches I found where people have asked the same question, but no confirmation of an attempt.
I will post my results for the next guy.

 

[smokeonthewater]

Re: Using 7 way round trailer plug as power source for electric winch

first "Irregardless" isn't a word.... sorry pet peave

second as I stated in the first reply this needs to be figured based on load and distance.... the package the winch comes in or the installation manual will plainly state the max amperage... then it is as easy as looking at a chart to determine the wire guage

I did originally say I would use at least 8 guage but I meant to say 4 and have edited it.

It is VERY much ok to put a battery on the trailer and charge from the truck and you are not the first to do this..... It is actually very common on car hauler trailers.... It is never done through the trailer connector unless just to charge the battery..... The circuit breaker is a thermal unit and will cycle on and off at a high draw to protect the wiring and connector.... Also as mentioned above voltage will drop considerably with a heavy load due to the resistance of the length of small wire.... The battery will be fine.... I would consider a small car battery though since they tend to be better build and not much more expensive than the lawn mower battery..... You also will have enough capacity to winch a couple times if you tow the trailer some time with another vehicle that can't charge the battery

 

[TerryMSU]

Re: Using 7 way round trailer plug as power source for electric winch

Again, mostly I concur. However, you might want to consider a deep cycle marine battery. This would be for reason of the posibility of deep cycling and also of vibration on the trailer. Also, you will want to make sure that you don't dunk the battery in the drink. The idea of an automatic reset circuit breaker sound like a really good one. That way, if you really run the battery down, eventually you will recharge the battery. One question, on the autoreset breakers, does anyone know how many cycles they will tolerate before failure? That might be the only concern I can see.

TerryMSU

 

[cr2k]

Re: Using 7 way round trailer plug as power source for electric winch

You could get a small garden tractor size sealed battery that would act as a "buffer" and your truck plug would charge the battery.

 

[H20Rat]

Re: Using 7 way round trailer plug as power source for electric winch

also keep in mind you aren't lifting the boat! Winching a 3000 pound boat onto your trailer does not take 3000 pounds of force. It might take a couple hundred at best. (any more and you REALLY need to back up more!)


As far as sustained... A couple minutes of winching would be an extreme case. (see above, back up more!) With your average 18' boat, you will only have a couple feet of line out, if the winch takes minutes to pull that, you have other problems. 30 seconds or less is probably more accurate.

 

[smokeonthewater]

Re: Using 7 way round trailer plug as power source for electric winch

anything over 5 seconds is sustained

 

[Starcraft Enterprise]

Re: Using 7 way round trailer plug as power source for electric winch

I hooked up a battery and inline amp meter to the winch to test the current. With the clutch disengaged and the motor running with no load it drew a steady 15 amps. When I engaged the clutch enough to similate a decent load it went to 20 amps. Then when I engaged it to stall it went to slightly over 30 amps. When I started it from a stall it buried the gage to I guesstimate 45 or 50 amps (30 amp gage).
This test was done with a deep cycle battery hooked directly to the winch with the 8 gauge winch jumper cables. So it does not take into account any voltage drop by the distance of traveling the vehicles electrical system through smaller conductors. DC power is alot more susceptible to voltage drop than AC power. The hot wire on the seven way plug is 12 gauge stranded and the negative is 10 gauge stranded. I assume the negative is 10 gauge because it also carries the load for the lights or trailer brakes or all of the above.

In conclusion, I believe the seven way power source would be capable of handling the load of this smaller winch under most operating conditions, but you would be pushing your luck. And in boating, murphy's law definetly applies.
I am going to take the safer route and mount a small battery to my trailer. I will be using the 7 way plug to maintain the charge on this battery. Then in the unlikely event I have to power winch with out being able to back into the water far as I want, I should still be able to retrieve my boat without breaking out the hand crank backup (roller bunk trailer).
After I have installed this setup and tested it a few times in the real world, I will try to find this post and update my results.
Thanks for everybody's opinions and advice.

 

[TerryMSU]

Re: Using 7 way round trailer plug as power source for electric winch

anything over 5 seconds is sustained

Smoke:

Where did the 5 seconds definition for "sustained" come from? Not trying to find fault, just wanting to know in case I want to use that number again.


Starcraft:

The difference is not AC vs. DC, but rather 115 Volts vs. 12 Volts. 6 volts out of 12 volts is 50% loss, 6 out of 115 is about 5% loss. Also, the low voltage stuff (12 volts) draws much more current for the same power and therefore the identical wire will drop much more voltage at 12 volts than at 115 volts. Your 50 amps at 12 volts would only be about 5 amps at 115 volts. (same power at different voltages means different currents.)

TerryMSU

 

[smokeonthewater]

Re: Using 7 way round trailer plug as power source for electric winch

Terry, I don't have a reference to cite on that... I chose that number based on personal experience with burning up various switches and relays and wires.... It doesn't take long at all for copper to reach temps that melt plastic and vinyl..... It was mainly to illustrate that a couple minutes or even 30 seconds is way longer than allowable at double the rated capacity on a circuit or contact


I didn't even think to mention the wiring included with the winch.... 8 guage and short tells us that 8 guage isn't heavy enough to run the full length of the vehicle....

Put a 15 amp thermal auto reset circuit breaker in a water proof junction box on your trailer and you will be good to go.

 

[Starcraft Enterprise]

Re: Using 7 way round trailer plug as power source for electric winch

Smoke:

Where did the 5 seconds definition for "sustained" come from? Not trying to find fault, just wanting to know in case I want to use that number again.


Starcraft:

The difference is not AC vs. DC, but rather 115 Volts vs. 12 Volts. 6 volts out of 12 volts is 50% loss, 6 out of 115 is about 5% loss. Also, the low voltage stuff (12 volts) draws much more current for the same power and therefore the identical wire will drop much more voltage at 12 volts than at 115 volts. Your 50 amps at 12 volts would only be about 5 amps at 115 volts. (same power at different voltages means different currents.)

TerryMSU

You are correct, I misquoted the "war of currents".

 

[dingbat]

Re: Using 7 way round trailer plug as power source for electric winch

Second - Irregardless of what the winch is rated for the actual current draw will be determined by what is actually be pulled. I assume he will be using the electric winch to pull a 1969 18' Starcraft Starchief, 120 I/O Mercruiser as in his signature. Not exacly an 8000 pound beast.

The weigh of the boat is for the most part irreverent. The current draw is going to be determined by the gear ratio of the winch. I can lift a car with a 10 HP motor and you can do it with a ? HP motor. Same weight, different current draws

 

[109jb]

Re: Using 7 way round trailer plug as power source for electric winch

The weigh of the boat is for the most part irreverent. The current draw is going to be determined by the gear ratio of the winch. I can lift a car with a 10 HP motor and you can do it with a ? HP motor. Same weight, different current draws

The current draw is dependent on the actual load on the motor whether geared or not. Maximum current draw will be at maximum motor load, minimum current draw will be the no-load current draw. The gear ratio only provides mechanical advantage to reduce the load on the motor.

My point, which is moot now, was that he could have tested the setup using a properly protected circuit (fused or circuit breaker) without fear of wiring damage. I did not know he had a amp-meter capable of 30+ amps. Most people don't. The fuse protected circuit would have given him an idea of current draw without a meter for the price of a few fuses.

This is an AC example and a bit different but you will get the idea. I have a Miller welder that says it needs a 50 amp breaker which would mean 6 gauge wire. Quite frankly the 6 gauge flexible cord (So I could roll it anywhere in my shop) was way too expensive but I got 10 gauge cheap. The 10 gauge cord is on a properly sized 30 amp breaker so there isn't a danger of overloading the wire. I've never blown the breaker but I remember to not operate the welder at its maximum. Works fine.